Re: [PATCH 01/16] path: refactor `repo_common_path()` family of functions

> The functions provided by the "path" subsystem to derive repository
> paths for the commondir, gitdir, worktrees and submodules are quite
> inconsistent. Some functions have a `strbuf_` prefix, others have
> different return values, some don't provide a variant working on top of
> `strbuf`s.
> 
> We're thus about to refactor all of these family of functions so that
> they follow a common pattern:
> 
>   - `repo_*_path()` returns an allocated string.
> 
>   - `repo_*_path_append()` appends the path to the caller-provided
>     buffer while returning a constant pointer to the buffer. This
>     clarifies whether the buffer is being appended to or rewritten,
>     which otherwise wasn't immediately obvious.
> 
>   - `repo_*_path_replace()` replaces contents of the buffer with the
>     computed path, again returning a pointer to the buffer contents.
> 

> diff --git a/path.h b/path.h
> index 5f6c85e5f8..3c75495e1a 100644
> --- a/path.h
> +++ b/path.h
> @@ -25,22 +25,20 @@ char *mkpathdup(const char *fmt, ...)
>  	__attribute__((format (printf, 1, 2)));
>  
>  /*
> - * The `strbuf_git_common_path` family of functions will construct a path into a
> + * The `repo_common_path` family of functions will construct a path into a
>   * repository's common git directory, which is shared by all worktrees.
>   */
> -
> -/*
> - * Constructs a path into the common git directory of repository `repo` and
> - * append it in the provided buffer `sb`.
> - */
> -void strbuf_git_common_path(struct strbuf *sb,
> -			    const struct repository *repo,
> -			    const char *fmt, ...)
> +char *repo_common_path(const struct repository *repo,
> +		       const char *fmt, ...)
> +	__attribute__((format (printf, 2, 3)));
> +const char *repo_common_path_append(const struct repository *repo,
> +				    struct strbuf *sb,
> +				    const char *fmt, ...)
> +	__attribute__((format (printf, 3, 4)));
> +const char *repo_common_path_replace(const struct repository *repo,
> +				     struct strbuf *sb,
> +				     const char *fmt, ...)
>  	__attribute__((format (printf, 3, 4)));
> -void repo_common_pathv(const struct repository *repo,
> -		       struct strbuf *buf,
> -		       const char *fmt,
> -		       va_list args);
>  
>  /*
>   * The `repo_git_path` family of functions will construct a path into a repository's
> @@ -243,6 +241,12 @@ struct strbuf *get_pathname(void);
>  #  include "strbuf.h"
>  #  include "repository.h"
>  
> +/* Internal implementation detail that should not be used. */
> +void repo_common_pathv(const struct repository *repo,
> +		       struct strbuf *buf,
> +		       const char *fmt,
> +		       va_list args);
> +